The Olf Trafford club have offered the Chilean a four-and-a-half-year contract with an annual income of £27million before tax, or just over £500,000 each week. His contract at Arsenal is due to expire in the summer.

With a transfer fee, signing-on lump sum and an agent's fee likely to be involved, it means United could face an overall outlay of over £150m should they secure a deal for the former Barcelona player.